U.S. patent number 5,839,196 [Application Number 08/887,599] was granted by the patent office on 1998-11-24 for wrenchless collet for surgical blade.
This patent grant is currently assigned to Linvatec Corporation. Invention is credited to A. Frank Trott.
United States Patent |
5,839,196 |
Trott |
November 24, 1998 |
Wrenchless collet for surgical blade
Abstract
A wrenchless collet for attaching a surgical saw blade to an
oscillating handpiece. The collet is provided within a housing
attached to the handpiece and contains a clamping means for holding
the blade and a bi-stable operating mechanism capable of holding
the clamping means in either an open position to receive the blade
or in a closed position to hold the blade for use with the
handpiece. The bi-stable operating mechanism is activated into
either position by simply being pushed in one direction or another.
In one embodiment, the bi-stable operating mechanism comprises a
shaft which may be positioned to one axial extreme or the other and
which is held in the chosen position by a spring which frictionally
engages the collet housing to maintain the clamping means in either
an open or closed position.
Inventors: |
Trott; A. Frank (Largo,
FL) |
Assignee: |
Linvatec Corporation (Largo,
FL)
|
Family
ID: |
24188491 |
Appl.
No.: |
08/887,599 |
Filed: |
July 3, 1997 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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548351 |
Nov 1, 1995 |
5729904 |
|
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Current U.S.
Class: |
30/339;
606/178 |
Current CPC
Class: |
B23D
51/10 (20130101); A61B 17/142 (20161101); A61B
2017/00477 (20130101) |
Current International
Class: |
B23D
51/10 (20060101); A61B 17/14 (20060101); B23D
51/00 (20060101); A61B 17/00 (20060101); A61B
017/14 () |
Field of
Search: |
;30/339,392-394,166.3
;279/86,97,141 ;606/82,178 ;83/697,698.71,699.21 ;403/322,327 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Article Entitled New Wrenchless Collet for Hall Large Bone
Oscillating Saws, Zimmer, Inc. Jul. 22, 1991, 2 pages..
|
Primary Examiner: Watts; Douglas D.
Attorney, Agent or Firm: Warzecha; Gene
Parent Case Text
This is a divisional application of application Ser. No.
08/548,351, filed Nov. 1, 1995 now U.S. Pat. No. 5,729,904.
Claims
What is claimed is:
1. A wrenchless collet for holding a cutting device comprising:
a housing:
clamp means within said housing for holding said cutting device,
said clamp means being movable relative to said housing, having an
axis and adapted to exert a clamping force on said cutting device
parallel to said axis and further comprising:
a first, axially stationary clamping surface:
a second, axially movable clamping surface, said second clamping
surface movable to either an open position in which it is spaced
from said first clamping surface or a closed position in which it
is urged toward said first clamping surface:
bi-stable clamp holding means for selectively holding said clamp
means in either said open position or said closed position
comprising:
a shaft connected to said second, axially movable clamping surface,
said shaft having a first end and a second end, said first and
second ends comprising
respective first second shaft pushing members;
a spring biasing means for providing a force;
a rolling member retaining mechanism comprising at least one
rolling member and carrier means axially movable relative to said
shaft for rotatably holding said rolling member adjacent said
shaft;
a first recess in said shaft associated with and adapted to receive
a portion of said rolling member therein, said first recess having
first and second axially spaced and oppositely directed tapered
sides for receiving from said rolling member axially directed force
from said spring means;
spring force receiving means interposed between said spring biasing
means and said carrier means for urging said carrier means axially
in said second direction to thereby urge said rolling member into
said first recess and partially axially against one of said tapered
sides thereof to hold said shaft in one of said open or closed
positions; and
a second recess in said housing associated with and adapted to
receive a portion of said rolling member therein, said second
recess having first and second oppositely directed tapered sides
and adapted to receive said rolling member when axial motion of
said shaft causes said rolling member to roll out of engagement
with said first recess, said second recess being angularly
juxtaposed to said first recess and situated at a greater radial
distance from said axis than said first recess, said second recess
for receiving said rolling means when said shaft is axially moved a
predetermined amount to roll said rolling member sufficiently to
place it partially into said second recess, and for urging said
rolling member against said shaft to frictionally retain said shaft
in the other of said open or closed positions.
2. A wrenchless blade collet according to claim 1 wherein said
rolling member comprises a cylindrical roller.
3. A wrenchless blade collet according to claim 1 wherein said
rolling member comprises a spherical member ball.
4. A wrenchless collet according to claim 1 wherein said first
recess is an annular groove having a first predetermined diameter
and said second recess is an annular groove having a second
predetermined diameter.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to blade attachment mechanisms for
surgical saws. More particularly, the invention relates to
wrenchless chuck or collet which can secure a surgical device such
as a saw blade to a drive means without any additional tools.
2. Description of the Prior Art
It is often necessary to use powered tissue cutting tools in order
to perform surgical procedures. Such tools generally comprise a
handpiece which cyclically moves a tissue cutting device such as a
blade or burr in some oscillating or reciprocating manner. The
handpiece generally includes a pneumatic or electric drive motor
having an output shaft to which the cutting device is attached, the
shaft being axially aligned with a drive axis of the handpiece. As
used herein, the term "drive axis" refers to the axis of the motor
output shaft through which power is delivered from the motor. The
handpiece may be a "pencil" type handpiece in which the body is
elongated and the drive axis is aligned with the axis of the body
or a pistol-grip type of handpiece in which the drive axis is
aligned in a chosen direction relative to the grip. The drive motor
of the handpiece produces a driving force which reciprocates the
output shaft and cutting device either longitudinally, i.e.
linearly along the drive axis (like a saber saw), or arcuately in a
plane perpendicular to the drive axis. Handpieces utilizing the
former type of action are generally referred to as reciprocating
saws while those utilizing the latter action are generally referred
to as oscillating saws. In some cases an oscillating saw may
transfer the oscillating drive motion so that it is cyclical within
a plane parallel to the axis of the elongated body of the
handpiece. A sagittal saw is a type of oscillatory saw in which the
cyclical reciprocating action is in a plane aligned with the drive
axis.
In all instances, numerous tissue cutting blades or burrs or other
devices (all collectively referred to herein as "blades") are
adapted to be secured to the handpiece via a chuck or collet
mechanism which is utilized to selectively attach and release a
desired blade. A variety of different cuts can be made with a
single saw depending upon the shape of the blade. For oscillating
saws, the blades are often in the form of a flat, elongated body
having a cutting edge (e.g. teeth, abrader, etc.) at one end and a
hub at the other end, the hub being shaped and adapted to fit the
particular collet. Such flat blades are used to make cuts in a
plane perpendicular to the drive axis. An oscillating saw may also
be used for effecting cuts in a plane parallel to the handpiece
axis by attaching a transverse hub to a flat blade.
Many blade collets utilize a threaded stud axially extending from
the output shaft and a nut adapted to engage the stud to clamp the
blade hub to the handpiece. These collets generally require the use
of a separate wrench to turn the clamping nut. U.S. Pat. No.
5,237,884 (Seto) shows a variety of conventional tool-requiring
chuck mechanisms in the form of a threaded shaft which is turned to
tighten against a clamping plate and saw blade. Since it is
desirable to avoid extra tools in a surgical setting, some collets
eliminate the need for a separate tool by utilizing a nut (e.g. a
wingnut) that can be manipulated without tools. Other collet
designs utilize a spring actuated, longitudinally movable clamping
head having longitudinally extending locking pins for engagement
with corresponding holes in the blade hub. The clamp head in such
designs is movable to place the collet into an open position for
receiving a blade and into a closed position for clamping the blade
between the head and a base surface. Such designs are referred to
herein as "wrenchless" designs and are generally preferable to
other chuck or collet mechanisms which require the use of separate
tools. The terms "chuck" and "collet" are used interchangeably
herein.
Yet another wrenchless collet design utilizes a spring actuated
clamping plate to frictionally engage a surgical blade. In many
cases projecting locking pins extend from a clamping surface to
produce a positive engagement with holes in the blade. The blade
clamp is momentarily movable by manual pressure directed to
compress the spring to an open position for receiving a blade.
Release of the manual pressure enables the spring to close the
clamp. Such collets are difficult to clean and sterilize due to the
need for the spring to be manually held in a compressed position
while a blade is inserted or removed or when the collet is
cleaned.
U.S. Pat. No. 5,265,343 (Pascaloff), assigned to the assignee
hereof, discloses a bi-stable type of wrenchless collet which
enables the blade clamp to stay in the open or closed position. The
ability to stay open without manual pressure facilitates the
loading, cleaning and sterilization of the device. However, this
design does not easily lend itself to all types of surgical saws or
to miniaturization. Accordingly, there is a need for a bi-stable
wrenchless collet adaptable to small surgical instruments.
In the case of oscillating or sagittal surgical saws used with
conventional flat blades oscillating in a plane aligned with or
parallel to the axis of a pencil-type handpiece, the collet
mechanism must be adapted to apply a force to the blade hub in a
direction perpen-dicular to the handpiece axis. For microsurgical
procedures such as oral-maxillofacial, ear-nose-throat (ENT) and
other procedures in confined areas, the size of the collet must be
minimized as much as possible to improve the surgeon visualization
of the surgical site. The challenge is to provide as small a collet
as possible while providing as much blade holding force as possible
while also enabling the collet to stay open for sterilization or
loading.
A wrenchless collet chuck in the form of a pushbutton is shown in
U.S. Pat. No. 5,383,785 (Brugger) as part of a dental tool. The
collet chuck is a hollow cylindrical member with axial slots spaced
along the body of the member such that adjacent slots are open at
opposite ends of the member in an alternating pattern. The arcuate
portions of the cylindrical member between the slots act as
clamping elements for holding a tool in axial alignment with the
hollow cylinder. A conical control surface is moved by the
pushbutton to move the clamping elements radially. This device is,
however, not only unsuitable for holding blades perpendicular to
the chuck axis but is also unable to maintain an open position
without a user having to continually push and hold the button
open.
Another representative wrenchless collet is shown in U.K. Patent
Application 2,195,274. This device utilizes a plurality of
circumferentially arranged locking balls which are biased radially
inwardly against an axially aligned tool shaft.
It is an object of this invention to provide a blade collet that
does not require a separate tool for its operation.
It is another object of this invention to produce a wrenchless
collet for holding a surgical device to a drive mechanism.
It is a further object of this invention to produce a wrenchless
blade collet for holding a flat surgical saw blade on an
oscillating or sagittal saw.
It is yet another object of this invention to produce a wrenchless
blade collet having a minimal size in order to enable its use in
microsurgical devices.
It is another object of this invention to provide a blade collet
that is easily operated and cleaned.
It is also an object of this invention to provide a wrenchless
blade collet which is bi-stable, i.e. having two states such that
the collet can be actuated to and stay in either an open position
or a closed position by a pushing motion.
It is yet another object of this invention to produce a collet
system adapted to securely hold a tissue cutting device to an
oscillatory saw.
It is also an object of this invention to produce a wrenchless and
adapterless system for securing a surgical blade to a powered
handpiece.
It is another object of this invention to produce a system for
attaching tissue cutting devices to powered handpieces without the
necessity for auxiliary tools.
SUMMARY OF THE INVENTION
These and other objects of this invention are achieved by the
preferred embodiment disclosed herein which is a wrenchless collet
for holding a cutting device comprising a blade clamp means in the
form of a first, axially stationary clamping surface and a second,
axially movable clamping surface. The second clamping surface is
movable to either an open position, in which it is spaced from the
first clamping surface, or a closed position in which it is urged
toward the first clamping surface. A clamp holding means is
provided for holding the blade clamp in either the open position or
the closed position, the clamp holding means comprising a shaft
connected to the blade clamp means and a bi-stable biasing means
for acting on the shaft to urge it axially either in one direction
when the blade clamp is in the closed position or in the other
direction when the blade clamp is in the open position. In the
preferred embodiment, the bi-stable biasing means comprises a flat
V-shaped spring in the form of a unitary member having a central
bight portion and a pair of spring legs extending outwardly from
the bight portion. The spring is attached to the shaft so that the
spring legs normally have a predetermined width greater than the
diameter of said shaft. The bight portion is attached to the shaft
such that the spring legs lie substantially in a plane parallel to
said axis. The shaft and the spring legs slide in a bore which is
sized to enable the pair of spring legs to be compressed to a width
substantially equal to the diameter of the shaft when the blade
clamping means is in the open position. A spring leg expansion
means is provided for enabling the pair of spring legs to return
toward their normal, unbiased state, when the blade clamp means is
in the closed position.
The invention disclosed herein is also in the method of selectively
attaching a cutting device to a surgical handpiece comprising the
steps of providing a wrenchless collet having a first clamping
surface member and a second clamping surface member, the members
relatively movable between a closed position wherein they are
aligned such that a cutting device may be held between the members
and an open position wherein they are spaced and a cutting device
may be inserted or removed therefrom. A clamp holding means is
provided to hold the wrenchless collet either open or closed. A
user accessible means is secured to the first clamping surface
member to push it either toward or away from the second clamping
surface member. The wrenchless collet is selectively opened by
pushing the user accessible means in a first direction to move the
first clamping surface member axially in one direction or
selectively closed by pushing the user accessible means in a second
direction to move the first clamping surface member axially in an
opposite direction.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevation view, in cross-section, of the distal
end of a sagittal saw showing one embodiment of the invention in a
closed position.
FIG. 2 is a cross-sectional view of FIG. 1 taken along the line
2--2.
FIG. 3 is an exploded view of a component part of the embodiment of
the invention shown in FIG. 1.
FIG. 4 is a plan view of another component part of the embodiment
of the invention shown in FIG. 1.
FIG. 5 is a cross-sectional view of FIG. 4 taken along the line
5--5.
FIG. 6 is a view of FIG. 1 showing the embodiment in an open
position.
FIG. 7 is a diagrammatic view in cross-section of another alternate
embodiment of the invention.
FIG. 8 is a plan view of a component part of FIG. 7.
FIG. 9 is an alternate embodiment of the part shown in FIG. 8.
FIG. 10 is another alternate embodiment of the part shown in FIG.
8.
FIG. 11 is a side elevation view, in cross-section, of an alternate
embodiment of the invention in an open position.
FIG. 12 is a view of FIG. 11 showing the embodiment in a closed
position.
FIG. 13 is an exploded view of FIG. 11.
FIG. 14 is a side elevation view in cross-section of another
alternate embodiment of the invention in a closed position.
FIG. 15 is a view of FIG. 14 in an open position.
FIG. 16 is a diagrammatic view in cross-section of another
alternate embodiment of the invention in an open position.
FIG. 17 is a view of FIG. 16 in a closed position.
FIG. 18 is a side elevation view in cross-section of another
alternate embodiment of the invention in a closed position.
FIG. 19 is a view of the embodiment of FIG. 18 in an open
position.
FIG. 20 is an elevation view of a component of FIG. 18.
FIG. 21 is an alternate embodiment of a spring used in the
embodiment shown in FIG. 18.
FIG. 22 is a side elevation view in cross-section of another
alternate embodiment of the invention in an open position.
FIG. 23 is a side elevation view in cross-section of another
alternate embodiment of the invention in an open position.
FIG. 24 is a cross-section of FIG. 23 taken along the line
24-24.
FIG. 25 is a view of FIG. 24 showing the invention in a closed
position with a blade.
DESCRIPTION OF THE PREFERRED EMBODIMENT
As shown in FIGS. 1 through 6, a wrenchless blade collet 10
constructed in accordance with the principles of this invention is
mounted to the distal end of a powered surgical handpiece 12 such
as an oscillating saw or sagittal saw. Collet 10 is intended for
use with a flat surgical saw blade 14 and is designed to stay in
either a closed position (best seen in FIG. 1) in which it will
hold blade 14 so that it may be driven in an operative manner by
handpiece 12 (i.e. in either a sagittal or oscillating mode), or in
an open position (best seen in FIG. 6) to enable the blade to be
assembled with or removed from the collet, or to enable the collet
to be sterilized and cleaned.
Collet 10 comprises a housing 20 having an axis 21, a blade clamp
22 and a bi-stable clamp operating or holding mechanism 24 which,
in the first embodiment shown in FIGS. 1-6, is a toroidal,
overcenter biasing spring 26, best seen in plan view in FIG. 4. The
preferred embodiment of toroidal spring 26 comprises a single wire
formed into a star-like shape having a plurality of lobes 70, the
tips of which define an inner circular periphery 72 and an outer
circular periphery 74. Depending on the chosen design, both
circular peripheries and the spring body may be concentric and
co-planar when the spring is in its neutral state or the spring
body between these peripheries may be outside this plane (as
diagrammatically shown in FIG. 5). Nevertheless, the spring is
intended to exert a force in each of two states, i.e. opened and
closed, and in each of these states the collet will maintain the
set position. The term bi-stable is used to indicate that the
spring is able to hold the collet either open or closed. It is not
intended to mean the spring is stable in any position without
cooperative action with its housing. Thus, when placed in one of
its biased states and viewed from the side (as shown in FIG. 1) the
inner circular periphery 72 is situated in one plane P1
perpendicular to axis 21 while the outer circular periphery 74 is
situated in another, parallel plane P2. A similar, but reversed
arrangement is shown in FIG. 6 when the spring is in its other
biased state.
Housing 20 comprises upper and lower sections 20a and 20b,
respectively, situated in a bearing 27 at distal end 28 of
handpiece 12, and is connected (by means not shown) to a driver
means 29 which imparts to housing 20 (and thereby to blade 14) the
appropriate oscillating drive motion about axis 21. As best seen in
FIGS. 1 and 2, housing 20 has a top clamping surface 30 provided
with a plurality of annularly arranged projecting pins 32 intended
to be received within corresponding apertures 33 in the hub or
proximal end of blade 14. The pins and apertures may be circular in
cross-section as shown, conical, rectilinear as shown in Des. U.S.
Pat. No. 362,065 assigned to the assignee hereof, or may have any
other suitable cross-section.
Bi-stable clamp operating mechanism 24 comprises a shaft 40 having
ends 44 and 48, the shaft extending through bore 42 of housing 20
to provide a pushing member at each end. The shaft is provided with
an enlarged, transverse clamping head 43 at end 44 and an enlarged
transverse pushbutton 46 at the other end 48. In the preferred
embodiment, head 43 is at all times parallel to surface 30 although
it will be understood that some other relationship (e.g. conical
interface, contoured, etc.) may also be used within the scope of
this invention. As will be understood below, both the clamping head
and the pushbutton serve as pushing members to alternately push
shaft 40 in one axial direction or the other. In the preferred
embodiment, clamping head 43 is axially movable relative to the
shaft axis while surface 30 is axially stationary. The shaft and
bore may be keyed or provided with noncircular cross-sections to
keep head 43 from rotating relative to surface 30. Since pushbutton
46 is enlarged and attached to end 48, it prevents travel of shaft
40 beyond a predetermined point and makes it easy for a user to
push on shaft 40 in an activating direction aligned with axis 21 to
open the blade clamp. The large sizes of the clamping head and the
pushbutton facilitate the use of the device by providing a tactile
indication to enable a user to merely push the shaft at one end or
the other.
Shaft 40 is provided with an inner, annular V-shaped recess in the
form of groove 60 interposed between ends 44 and 48 and intended to
operate with bi-stable operating mechanism 24 by receiving the
inner circular periphery 72 of toroidal spring 26. As shown in FIG.
3, the preferred embodiment of shaft 40 is formed of two
cylindrical extensions 22a and 22b joined by screw 50 and defining
groove 60 at their juncture. Similarly, housing 20 is provided with
an outer, annular groove 62 intended to receive the outer circular
periphery 74 of toroidal spring 26. The interior 42 between grooves
60 and 62 serves as an expansion chamber for the spring and its
shape is somewhat dependent upon the characteristics of spring 26.
The diameters of grooves 60 and 62 are chosen such that spring 26
can maintain a biasing force on groove 60 and, therefore, on shaft
40. This force must be sufficient to bias shaft 40 downwardly in a
closed position as shown in FIG. 1 to thereby urge clamping member
43 towards clamping surface 30 to thereby retain it and blade 14
adjacent posts 32 and surface 30. Similarly, when the clamp is
opened, the force must be enough to hold it open as shown in FIG.
6. The interaction of the spring and its associated structures
serves to selectively transfer and direct the spring force to the
shaft and ultimately to the clamping surfaces. It will be
understood that as transverse pushbutton end 46 is pushed upwardly
relative to FIG. 1 to the position shown in FIG. 6, the force of
toroidal spring 26 will be overcome and it will be compressed over
its neutral "center" position. At that point, the spring force is
redirected to place the spring into the position shown in FIG. 6 in
which it will bias shaft 40 upwardly to keep clamping surface 43
spaced from clamping surface 30, thereby holding blade clamp 22 in
an open position.
The inner surface 80 of pushbutton 46 may be provided with a
roughened surface such as a plurality of projections 82 which
facilitate the sterilization of collet 10 in the open position. The
projections are only shown by way of example in FIG. 1 while FIGS.
3 and 5 show surface 80 as being flat, albeit recessed from an
annular lip 84 which may have radially extending channels
therethrough (not shown).
Another simplified variation of the previous embodiment is shown in
FIG. 7 as collet 90 employing a toroidal, overcenter spring 92
having two stable states, best seen in phantom in FIG. 7. Collet 90
differs from collet 10 in that it is housed in a unitary housing
and the junction between the shaft and spring is assembled
differently. Spring 92 is a formed wire similar in function to
spring 26 and having similar inner and outer circular peripheries,
but with a different profile in plan view, as best seen in FIG. 8.
The radially outward arcuate segments 94 enable use of
complementarily shaped spaced arcuate apertures (not shown) within
the groove 96 in the wall of housing 98 rather than a continuous
groove similar to groove 62 of FIG. 1. An alternate embodiment of
spring 92, shown in FIG. 9 as spring 92a, is formed of a unitary
piece of material having a central bore 99 which defines the inner
periphery. FIG. 10 shows another spring 92b formed of a
multi-coiled, single piece of wire. In operation, the clamp head 97
of collet 90 is held open, when spring 92 is biased to one of its
bi-stable states A, and closed when the spring is in the other of
its bi-stable states B. Both states are shown in phantom while an
unstable, transition position of spring 92 is shown in full lines.
The shape of the spring body in these views is merely intended to
show that the spring shape changes as the shaft is moved, and is
not intended to be an exact depiction of spring shape.
As shown in FIGS. 11, 12 and 13, an alternate embodiment of the
invention comprises a wrenchless collet 100 attached to the distal
end of a surgical handpiece 110 having an oscillating drive member
112. Collet 100 is similar in function to collet 10 and differs in
the embodiment of the invention by which the blade clamp is held in
either the open or closed position.
Collet 100 comprises a housing 120 having an axis 121, a bi-stable
blade clamp 122 and a dual-action, rolling member retaining
mechanism 124. Housing 120 has upper and lower portions 120a and
120b, respectively, each of which has longitudinally extending
cylindrical walls 130a and 130b, respectively. Upper housing
section 120a is provided with a flange 150 and lower housing
section 120b is provided with a flange 152, both flanges serving to
retain a spring 154 therebetween. In the embodiment shown, rolling
member retaining mechanism 124 utilizes spherical members rather
than cylindrical members and comprises a cylindrical ball carrier
126 formed integrally with lower housing 120b, surrounding shaft
140 and retaining a plurality of circumferentially spaced locking
balls 128. The radial thickness of the cylindrical wall 130a of
ball carrier 126 is substantially equal to the size of the annular
gap between shaft 140 and the cylindrical wall 130b of upper
housing portion 120a. Shaft 140 has a first annular groove 142 into
which balls 128 are partially received when the blade clamp is in
its closed position (FIG. 12) and wall 130b has a second annular
groove 144 into which balls 128 are partially received when the
blade clamp is in its open position (as best seen in FIG. 11). It
will be noted that annular groove 142 has two oppositely facing,
axially spaced tapered side surfaces such that any axial force
imparted by balls 128 to the tapered surfaces will move the shaft
axially. Groove 144 also has two oppositely facing tapered side
surfaces to receive the balls 128 and transfer compressive force
from the housing to the shaft. It will be noted that lower housing
portion 120b travels a predetermined axial distance between the
open and closed positions in order to accommodate the rolling
motion of balls 128. The diameter of each of the locking balls 128
is substantially equal to (or only slightly greater than) the size
of the spaces within which the balls are intended to move. Thus, at
one extreme of axial motion as shown in FIG. 12 the diameter of the
locking balls is equal to the distance between the radially
innermost side of wall 130b and the floor of annular groove 142. As
the lower tapered surface of groove 142 pushes the ball upwardly in
the process of moving collet 100 from the closed position to the
open position shown in FIG. 11, the ball rolls within the space
between the radially innermost side of wall 130b and the floor of
annular groove 142 until it clears the lower edge of annular groove
144. At this point, the ball naturally rolls into this groove as
the shaft is moved further into the open position until the locking
balls are captured between the floor of annular groove 144 and the
radially outermost surface of shaft 140 as shown in FIG. 11. The
frictional engagement at this point maintains the collet in an open
position.
The grooves 142 and 144 may be replaced by one or more coplanar
recesses (not shown) which are arranged angularly about axis 121 in
order to be aligned to receive a locking ball associated
therewith.
Another embodiment of the invention is shown in FIGS. 14 and 15 as
collet 200 which operates similarly to collet 100 except that the
spring 254 is located adjacent the shaft. Shaft 240 has an
intermediate groove 242 which receives balls 228 in the closed
position. Ball carrier 226 holds balls 228 and moves within the gap
between shaft 240 and body 212. The latter is provided with groove
244 to receive balls 228 in the open position.
Another embodiment of the invention is shown in FIG. 16 as collet
300 shown in an embodiment adapted to axially retain an elongated
shaft 302 such as a drill bit or other axially elongated tool. This
embodiment operates similarly to that shown in FIGS. 14 and 15. The
clamping mechanism of collet 300 provides a tool retention force in
a direction perpendicular to the axis 304 of the collet shaft in
order to frictionally engage tool shaft 302 in axial alignment with
the collet shaft.
Another embodiment of the invention is shown in FIGS. 18 through 21
as collet 400 comprising blade clamp 401, shaft 402 and spring 404.
Other components are similar to previous embodiments and need not
be separately explained here. Shaft 402 has cylindrical body 410, a
clamp head 406 at one end thereof and a screw-receiving bore 408 at
the other end. The end of shaft 402 adjacent bore 408 is provided
with a transverse axial slot 412 and the closed end of the slot is
provided with a bore 414 perpendicular to the slot. The
cross-section of body 410 is shaped and keyed to fit in bore 418
within which the shaft moves without rotation. Spring 404 comprises
a flat, pre-formed spring member 420 having a central bight portion
422 from which spring legs 424 and 426 extend. The spring legs
extend in generally the same direction relative to bight portion
422 so spring 404 has a general "V" shape. A simple yet effective
spring 404 may be formed from a length of wire shaped to have a
bight portion 422 in the form of a simple bend or with one or more
coiled loops 430 as shown. Spring legs 424 and 426 can remain on
the same side of the spring axis 432 from which they originate (as
best seen in FIG. 18). Alternatively, an embodiment such as spring
404a could be produced such that spring legs 424a and 426a extend
from bight portion 422a and cross the axis 432 as best seen in FIG.
21. Bore 414 is adapted to receive pin 416 which retains spring 404
within transverse slot 412.
While spring legs 424/426 and 424a/426a are normally in a "V"
configuration as best seen in FIGS. 18 and 19, the curvature of the
legs may vary from some curve as shown in FIG. 18 to fairly
straight as shown in FIG. 21. The curvature of the spring legs
affects the degree of travel of shaft 402 and the clamping force.
Starting from the closed position shown in FIG. 18, it will be
understood that as the pushbutton end of the shaft 402 is pushed
upwardly, the inside edges 440 and 442 of the housing (actually
opposite sides of the bottom circular edge of bore 418) push the
spring legs inwardly such that when pushbutton 443 abuts the bottom
end of the housing, the radially outermost surfaces 444 and 446 of
spring legs 424 and 426 contact the inside wall of bore 418 as best
seen in FIG. 19. The frictional engagement at these points holds
clamp head 406 open and the curvature imparted to legs 424/426
helps provide this force. Similarly, starting from an open position
as clamp head 406 is pushed downwardly, the contact points 444 and
446 eventually clear edges 440 and 442 and the natural spring force
of spring 404 will assist in its further downward motion. The
collet reaches its closed position before the spring legs are able
to reach their unbiased state so the spring can continue to apply a
clamping force. The curvature of the legs between points 444/446
and the central bight portion will affect the speed of the
spring-assisted downward motion as well as the ultimate clamping
force once the clamp head is closed.
Various channels and cut-outs may be provided to facilitate
cleaning and sterilization. For example, an axial channel 450 may
be provided in the clamp head to enable communication between slot
412 and the outside surface of clamp head 406. Similarly, a
plurality of annularly arranged throughbores 452 may be situated
within clamp head 406 above each pin location. Also, radial
cut-outs 454 may be provided to access the interior.
Another alternate embodiment of the invention is shown in FIG. 22
as collet 600 which incorporates a modified shaft 602 having an
intermediate clamp head 604 interposed between shaft ends 606 and
608. Shaft 602 is attached to a sagittal saw 607 and is adapted to
reciprocate within bore 610 of housing 612 although both of these
elements are split into upper and lower portions 610a/610b and
612a/612b, respectively. While previous embodiments were one-sided,
single bearing designs, this arrangement enables each bore portion
610a and 610b to be provided with its own bearing 614 and 616,
respectively, to more efficiently dissipate heat where high
cyclical speeds are required. Clamp head 604 is shown in FIG. 22 in
an open position spaced above clamp surface 620 and pins 622 on
drive element 624. Spring 630 is similar to spring 404 and operates
adjacent a hardened thrust collar or bushing 632 secured to rim of
bore 610b adjacent the spring legs in order to enhance performance
of the invention. Spring 630 acts like the previously described
springs of similar design to place and hold clamping head 604 in a
closed position (not shown) to hold a blade (not shown) between
head 604 and clamping surface 620.
A variation of this embodiment is shown in FIGS. 23-25 as collet
700 attached to sagittal saw 702. The structure of collet 700 is
similar to that of collet 600 with slight variations. For example,
the housing within which collet 700 is situated is a pair of
integral extensions of the saw body. Collet 700 comprises a shaft
704 having an enlarged end 706 and a smaller other end 708 to
provide a tactile indication of which end to push to open or close
the collet. In the embodiment shown, pushing the large end opens
the collet although the sizes of the ends could be reversed.
Similar tactile indicators may clearly be used with all of the
other embodiments disclosed herein. Shaft 704 is cylindrical with a
generally circular cross-section which has two flattened sides 710
and 712, best seen in FIG. 24, which enable shaft 702 to slide
without rotating within a generally rectangular aperture 714 in
driver 716. A shoulder 718 is provided to receive a similar
rectangular aperture 720 in plate 722 and a threaded keeper 724 is
used to secure plate 722 adjacent shoulder 718 of shaft 704. Plate
722 serves as the clamp head in this design. A pair of bearings 726
and 728 enable shaft 704 to oscillate within aligned apertures 730
and 732 at the distal end of saw 702. A threaded cap 734 holds the
assembly together.
As shown in FIG. 24, spring 740 is aligned in a plane transverse to
the axis of saw 702 and is supported by spring pin 742 within slot
744 of shaft 704. A central bore 746 and aperture 748 in the keeper
facilitate cleaning and sterilization of the various components. In
the open position shown in FIG. 24, the spring legs rest against
bushing 750 which is shaped to provide bearing points for the
spring legs as the spring moves towards the closed position shown
in FIG. 25. A blade 752 is retained as shown when collet 700 is in
the closed position.
The relative orientations of the components shown in the various
embodiments may be altered within the scope of this invention. For
example, the spring in the embodiment of FIGS. 10 and 11 may be
repositioned so that the locking balls are between the spring and
the clamping head. Such changes might alter the specific function
of some components but would not vary the basic concept disclosed.
Furthermore, other arrangements of component parts may provide
further embodiments. For example, using any of the embodiments with
a motion transferring linkage to make the force of the clamping
head be directed perpendicular to the axis of the shaft may enable
one to produce a collet in which the activating motion is axially
aligned with the shaft while the clamping force is perpendicular
thereto, albeit applied at a point spaced from the axis, thereby
enabling the saw blade body to be axially aligned with the
handpiece but spaced from the axis.
It will be understood by those skilled in the art that numerous
improvements and modifications may be made to the preferred
embodiment of the invention disclosed herein without departing from
the spirit and scope thereof.
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